78 INSTINCTIVE BEHAVIOUR 
was below, we drew it back to a little distance. She came out, 
and we both repeated our operations four times—she running 
down into the nest, always after getting the grasshopper into 
position, and we as regularly drawing it away. The fifth 
time she changed her plan, seized it by the head and backed 
into the nest with it. The next day, at the fourth trial, she 
straddled it and walked head first into the nest with it: and 
on the fourth day, at the eighth trial, she backed in with it as 
on the second day.” These interesting observations show 
that the wasp has sufficient intelligence to modify her pro- 
cedure in accordance with an unwonted situation. The 
“consecutive necessity,” as it has been termed, has a potent 
influence, but is not absolute. 
Fabre notes a case of similar consecutive necessity in the 
case of the mason bee, Chalicodoma. If while a bee is pro- 
Visioning its nest with honey and pollen the structure be 
destroyed, she sometimes breaks open a completed cell, and, 
having done so, goes on bringing more provision, though the 
cell already contains a sufficient store of food ; and only when 
she has completed the superfluous storing does she deposit her 
egg and seal up the cell. So, too, when the cell is removed 
im an early stage of construction, and another completed cell 
already partially stored is substituted, the bee, instead of simply 
adopting the new cell, goes on building until the cell is as 
much as one-third beyond the usual height ; then, and not till 
then, does she proceed in due course to the next stage of the 
instinctive procedure, the provisioning of the cell. 
From our general knowledge of animal nature, we should 
expect to find parasitic forms ready to take advantage of the 
material stored by such insects as the solitary wasps and the 
mason bees. It is said that Chalicodoma provides nourishment 
to the larvee of some sixteen unbidden guests. A parasitic 
bee (Stelis nasuta) breaks open a closed cell, and, after deposit- 
ing its eggs, seals it up again with mortar. Since her eggs 
and larvee develop more rapidly than those of the mason bee, 
they are first served with the store of provision, while the 
rightful owner is done out of its inheritance. By a curious 
